the dissociation of nickel hydroxide is follows:
![ni(oh)_2 > ni^2^+ + 2 oh^-](/tex.php?f=ni(oh)_2 > ni^2^+ + 2 oh^-)
![ksp for no(oh)2 = 5.5 * 10^-^1^6](/tex.php?f=ksp for no(oh)2 = 5.5 * 10^-^1^6)
![5.5 * 10^-^1^6 = s * (2 s)^2 = 4 s^3](/tex.php?f=5.5 * 10^-^1^6 = s * (2 s)^2 = 4 s^3)
![s^3 = 137.5 * 10^-^1^8](/tex.php?f=s^3 = 137.5 * 10^-^1^8)
![s = 5.14 * 10^-^6 = [oh^-]](/tex.php?f=s = 5.14 * 10^-^6 = [oh^-])
the concentration of hydroxide ion is
![5.14 * 10^-^6 = [oh^-]](/tex.php?f=5.14 * 10^-^6 = [oh^-])
the equilibrium constant value of nickel hydroxide is = 6.1 * 10^-^1^6 and thus equilibrium equation can be written as:
![k = [ ni^2^+] * [oh^-]^2](/tex.php?f=k = [ ni^2^+] * [oh^-]^2)
![6.1 * 10^-^1^6 = [ ni^2] * [5.14 * 10^-^6]^2](/tex.php?f=6.1 * 10^-^1^6 = [ ni^2] * [5.14 * 10^-^6]^2)
![[ ni^2^+] = 0.23 * 10^-^4 mol /l](/tex.php?f=[ ni^2^+] = 0.23 * 10^-^4 mol /l)
thus, concentration of ni is 0.23 * 10^-^4 mol /l